The native peoples of the Amazon in modern-day Brazil are thought to have originated from several waves of North Asian migration over the Bering Strait during the last Ice Age (about 10,000 years ago). Archeological evidence suggests some large settlements with complex social structures and a livelihood based on hunting, gathering, fishing, and basic agriculture. Indigenous Amazonians — who were divided into two sub-groups known as the Tupi and the Tapuia — first encountered Portuguese explorers in 1500. The native Amazonian population subsequently suffered from slavery, aggressive proselytization, forced migration, and destruction of their habitat due to the rubber trade. In recent years, the Brazilian government has passed laws protecting the culture and lands of indigenous groups. Native peoples of the region have cultivated the ecologically diverse resources of the rainforest for thousands of years; some tribes are well-known for hunting with blow darts dipped into the poison found on the skin of Amazonian frogs.